1. Field of the Invention
The present invention relates generally to a zoom lens apparatus, and more particularly to a zoom lens apparatus which is provided with a variable magnification lens group, an aberration correction lens group and a focus correction lens group.
2. Description of Related Art
A conventional zoom lens apparatus zooms an image by means of two movable lens groups including a variable magnification lens group and a focus correction lens group. The zooming performance has been recently improved by three movable lens groups further including an aberration correction lens group.
A cam cylinder (a cam member) is rotatably arranged on the lens barrel of the above-mentioned zoom lens apparatus. Three cam grooves are formed on the cam cylinder, and each cam groove is engaged with a cam pin (follower) provided in each movable lens group. The cam pins stick out through the cam grooves, and engage with straight grooves formed on a fixed cylinder, which is arranged on the periphery of the cam cylinder. Thus, when the cam cylinder is rotated, the variable magnification lens group, the aberration correction lens group and the focus correction lens group separately move both forward and backward along the optical axis due to the operation of the cam pins, the cam grooves and the straight grooves.
The conventional zoom lens apparatus, however, is provided with three cam grooves, which are formed on the cam cylinder, and thus, the cam cylinder is long and the zoom lens apparatus is large in size.